1. Field of the Invention
The present invention relates generally to needle devices for the injection and extraction of fluids. More specifically, the present invention relates to active needle devices such as macroneedles, microneedles, and macroneedle or microneedle arrays which have one or more active components providing additional functionality to the needle devices.
2. Relevant Technology
Micro instrumentation is a rapidly growing area of interest for a broad spectrum of applications. One particularly fast growing area is biomedical instrumentation where significant efforts are being made to develop micro biochemical analysis systems, physiological analysis systems, and drug delivery systems. A variety of manufacturing technologies are used to fabricate these micro systems, many of which are categorized under the set of technologies known as micromachining. The number of biomedical applications for micromachining technologies is rapidly growing. Since micromachining technologies are relatively new, there is an increasing set of manufacturing techniques and critical applications still to be addressed.
It is well known that needles are used to extract samples of substances from living tissue in order to analyze the substances for diagnostic purposes, or to deliver a drug or medicament. The majority of needles in use today are macroneedles, which have a relatively large diameter as compared to a blood cell and are on the order of millimeters (mm).
In many areas of biotechnology and medicine, there exists the need for fluid injection or extraction on a microscale; either for injection into a precise location, or for injecting or extracting small amounts of fluid. It is advantageous to be able to perform these injections or extractions with a minimal amount of tissue damage, and also with a minimum amount of discomfort and pain to patients. Microneedles and microneedle arrays are capable of performing these tasks. For example, microneedles and microneedle arrays can be used as precise injection/extraction needles in cell biology, as injection/extraction heads in a drug delivery system or microchemical factory, and as injection/extraction heads in microsurgery. Some of the smallest hollow needles that are currently available have inner diameters of over 200 μm. Prior micro-sized (sizes on the order of microns, where 1 micron=1 μm=10−6 m) needles include those disclosed in U.S. Pat. No. 5,457,041 to Ginaven et al., and U.S. Pat. No. 5,591,139 to Lin et al.
For some applications, it is desirable to inject small amounts of fluid; however, in other situations, larger amounts of fluid are required to be injected. Most of the prior systems do not have the capability to transmit larger amounts of fluid into a precise location. One of the methods used to address this problem is to fabricate an array of needles, as in U.S. Pat. No. 5,457,041 referred to hereinabove, which discloses an array of microneedles of about 20 needles by 20 needles, wherein the length of the needles is between 10 and 25 microns, and the spacing between needles is between about 5 and 20 microns.
In U.S. Pat. No. 5,591,139 referred to above, silicon-based microneedles are disclosed which are fabricated using integrated circuit processes. Various devices such as microheaters, mircrodetectors, and other devices can be fabricated on the microneedle.
Problems with prior microneedles include relatively poor mechanical durability. This is mainly due to the fact that such microneedles have been made out of etched silicon or out of chemical vapor deposited polysilicon, both of which have a tendency to be brittle and break easily.
In some cases, it is desirable to analyze the fluids being injected or extracted by the microneedle(s). Prior microneedles generally have been separate from the systems used to analyze (chemically, optically, or otherwise) the fluids. In these cases, having a separate analysis system can require additional equipment and is costly, complex, and inconvenient.
It would therefore be of substantial interest to develop a durable needle device which is capable of injecting or extracting precise quantities of fluids into specific locations with a minimal amount of tissue damage, and which has integrated sensing capabilities.